1. Field of the Invention
The present invention relates to a sensor device and an output characteristic switching method of the sensor device.
2. Description of the Related Art
A conventional pressure sensor device generally has one appropriate range with respect to the pressure range of a measured object.
However, for example, when the pressures of different ranges are detected with high accuracy at the time of a leak inspection executed in a sensor arrangement and the actual using time of the sensor device actually used in a system, the difference in the pressure of a measured object is large. Therefore, it is necessary to have two ranges in one sensor device.
In the pressure sensor device for coping with plural ranges, as shown in FIG. 10, upper and lower limit voltages are set in the relation of a pressure value and an output voltage and a returning operation is performed plural times therebetween. Thus, the pressure can be detected in the same resolution as small pressure even in the case of large pressure.
Otherwise, as shown in FIG. 11, a reference voltage setting terminal is arranged, and an analog voltage is inputted from an external device (a microcomputer, etc.). Thus, as shown in FIG. 12, characteristic lines every reference voltage are switched, and the pressure of a wide range can be detected in the same resolution.
However, in the case of FIG. 10, no actual pressure can be distinguished from the sensor output. Therefore, a problem exists in that there is a limit of the use. Namely, since the pressure value is indefinite from only the output voltage, it is necessary to specify the pressure value by further using another information from an external device (microcomputer, etc.). Further, in the cases of FIGS. 11 and 12, problems exist in that a DA converter is required in the external device (microcomputer, etc.) to set the reference voltage, and it is necessary to increase the number of dedicated wirings (reference voltage lines) by one.